This invention relates generally to aerospike engines and more particularly to aerospike engines having pulse detonation devices.
In a conventional rocket engine, fuel and oxidizer are pumped to a combustion chamber under extremely high pressure and burned to create a propulsive gas. This gas is exhausted through a nozzle, typically referred to as a de Laval or bell nozzle, which accelerates the gases to create propulsive thrust. As the vehicle powered by the rocket engine climbs, the exhaust plume expands outside the bell nozzle due to decreasing atmospheric pressure. Because the bell nozzle has a fixed geometry, it cannot adequately adapt to changing backpressure as the vehicle ascends through the atmosphere. Eventually, the nozzle becomes xe2x80x9cunderexpanded,xe2x80x9d resulting in propulsive efficiency losses.
An alternative approach is a linear aerospike engine, which uses two sloped nozzle surfaces in place of a conventional bell nozzle. The nozzle surfaces are open to the atmosphere and arranged in a V-shaped configuration. A series of small, independent combustion chambers is located along the upper edge of each of the nozzle surfaces. The combustion chambers are oriented such that hot exhaust gases are directed almost parallel to the nozzle surfaces to produce thrust. Unlike a bell nozzle, the exhaust plume from an aerospike nozzle surface is open on one side and thus free to expand. The open exhaust plume compensates for decreasing atmospheric pressure as the vehicle climbs and maintains optimum engine efficiency regardless of altitude and atmospheric pressure. With the combustor chambers mounted in rows along the width of the engine, steering a vehicle can be achieved by selectively throttling particular sets of the combustion chambers. For instance, throttling either the upper or lower row in a horizontally mounted engine will result in asymmetric thrust on one side of the vehicle and thus control pitch. Throttling either the left or right sides of both rows will control yaw.
Current aerospike engines rely on deflagration combustion systems whereby the combustion effects occur at relatively slow rates (i.e., less than the speed of sound within the combustible mixture) and at constant pressure. Detonation combustion, however, occurs at rates well in excess of the speed of sound and simultaneously provides a significant pressure rise. Because of the efficient thermodynamic cycle, it would be advantageous to implement aerospike engines with detonation-based propulsive devices.
The above-mentioned need is met by the present invention, which provides an aerospike engine having at least one nozzle surface and a plurality of pulse detonation devices mounted to the nozzle surface. Each pulse detonation device is oriented such that its combustion products a directed along the nozzle surface.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.